Proximity sensor not providing anticipated output

This is my first post - and my first attempt to build a RepRap - so a warm hello to all.

I've got to the point where I have made a few test prints, these have not stuck correctly to the bed so was playing around with temperatures to try to improve things.

Sadly the proximity sensor - the IR versions provided as part of the standard Huxley Duo - has stopped responding as intended. I managed to zero in all 3 planes, but any attempts to zero in x (or, somewhat catastrophically, Z) result in the printer jamming into end of travel.

When commissioning, the proximity sensor returned the anticipated value of 950ish in pronterface when a piece of paper was placed in front of the sensor, but this has apparently dropped to 250. The voltages for the sensor connections (taken from the proximity sensor board itself) are quite a bit away from the desired - I get around 0.6V instead of the anticipated 1.53V when a piece of paper is in front. The Yellow voltage is also a bit out, but the blue and green are OK suggesting the sensor is correctly powered. The duet itself appears OK from the tests I've run.

Have I somehow broken the proximity sensor? I've had a few nozzle blockages which have required taking the hot end apart, so I worry I've banged it in the process - the sensor was OK for quite a few aborted test prints.

Advice on what to try would be much appreciated. I've contacted support, but perhaps best to wean myself off their assistance!

One quick thing to check is that the sensitive face of the IR sensor (the black cuboid at the bottom of the sensor board) is still parallel to the bed. The sensor is mounted on legs, which can get bent if the sensor hits something.